Retransmission of data to or from a mobile station, MS, or user equipment, UE, is previously known. It is also known to use medium access control and radio link control layers of a UMTS protocol structure in acknowledged mode for dedicated, common and shared channels.
In acknowledged mode, retransmissions are undertaken in case of detected transmission errors not recovered by forward error control. This is also called automatic repeat request, ARQ. With ARQ, retransmissions can be undertaken unless a transmitted message is (positively) acknowledged or if it is negatively acknowledged. Generally there are time limits for the respective positive and negative acknowledgements to be considered.
Within this patent application, a radio network controller, RNC, is understood as a network element including a radio resource controller. Node B is a logical node responsible for radio transmission/reception in one or more cells to/from a User Equipment. A base station, BS, is a physical entity representing Node B.
With reference to FIG. 1, base stations >>BS 1<< and >>BS 2<< are physical entities representing Nodes B >>Node B 1<< and >>Node B 2<< respectively. Node B 1 and Node B 2 terminate the air interface, called Uu interface within UMTS, between UE and respective Node B towards the radio network controller RNC. In UMTS the interface between a Node B and an RNC is called Iub interface.
Medium access control, MAC, and radio link control, RLC, is used within radio communications systems like General Packet Radio Services, GPRS, and UMTS.
International Patent Application WO0021244 describes flow control operating in WT space, based upon measurements of number of packets (window, W) and round-trip time (time, T) for avoiding system underload/overload by adjusting packet sending rate. A terminal measures window size, round-trip time and packet losses for determining of its sending rate. Alternatively, the terminal is provided with explicit indicators of congestion status or sending rate from network nodes.
Canadian Patent Application CA02308937 discloses a method and apparatus for interconnection of flow-controlled communications. Flow control is performed by including status information in upstream direction of a bi-directional communication link revealing availability status of the channel in downstream direction. A scheduler selects channels for downstream data depending on their availability status.
International Patent Application WO0041365 demonstrates a method and system for credit-based data flow control where a receiver establishes a credit list and transfers a credit message to the sender. When the sender transfers data packets to the receiver, the credit outstanding is reduced. The sender transfers packets only as long as its credit is not consumed. With no credit available, the sender refrains from transmitting packets to the receiver until it achieves new credits.
U.S. Pat. No. 5,831,985 describes a method and system for flow control of communications over a fiber channel. A switch allocates connection line capacity to data sources in relation to their priority and credit available to the source.
3rd Generation Partnership Project (3GPP): Technical Specification Group Radio Access Network, UTRAN Overall Description, 3G TS 25.401 v3.6.0, France, March 2001, specifies in section 11.1 a general protocol model for UTRAN interfaces. In subsection 11.2.5 a model of a DSCH (Downlink Shared Channel) transport channel for co-incident and separate controlling and serving RNCs respectively. A DSCH is a downlink channel shared dynamically between UEs. It carries dedicated control or traffic data.
3rd Generation Partnership Project (3GPP): Technical Specification Group Radio Access Network, Radio Interface Protocol Architecture, 3G TS 25.301 v3.6.0, France, September 2000, describes in paragraph 5.6.5.3 a model of a DSCH, an RACH/FACH and a DCH in UTRAN.
FIG. 2 displays a simplified UMTS layers 1 and 2 protocol structure for a Uu Stratum, UuS, or Radio Stratum, between a user equipment UE and a Universal Terrestrial Radio Access Network, UTRAN. The radio interface includes three protocol layers:                physical layer L1,        data link layer L2 and        network layer L3.        
Two of the protocol layers (L1 and L2) are included in FIG. 2. The data link layer is split into four sub-layers: PDCP (Packet Data Convergence Protocol), BMC (Broadcast/Multicast Control), RLC (Radio Link Control) and MAC (Medium Access Control).
Radio Access Bearers, RABs, are associated with the application for transportation of services between core network, CN, and user equipment, UE, through a radio access network. Each RAB is associated with quality attributes such as service class, guaranteed bit rate, transfer delay, residual BER (Bit Error Rate), and traffic handling priority. An RAB may be assigned one or more Radio Bearers, RBs, being responsible for the transportation between UTRAN and UE. For each mobile station there may be one or several RBs representing a radio link comprising one or more channels between UE and UTRAN. Data flows (in the form of segments) of the RBs are passed to respective Radio Link Control, RLC, entities which amongst other tasks buffer the received data segments. There is one RLC entity for each RB. In the RLC layer, RBs are mapped onto respective logical channels. A Medium Access Control, MAC, entity receives data transmitted in the logical channels and further maps logical channels onto a set of transport channels. In accordance with subsection 5.3.1.2 of the 3GPP technical specification, MAC should support service multiplexing e.g. for RLC services to be mapped on the same transport channel. In this case identification of multiplexing is contained in the MAC protocol control information.
Transport channels are finally mapped to a single physical channel which has a total bandwidth allocated to it by the network. In frequency division duplex mode, a physical channel is defined by code, frequency and, in the uplink, relative phase (I/Q). In time division duplex mode a physical channel is defined by code, frequency, and time-slot. The DSCH, e.g., is mapped onto one or several physical channels such that a specified part of the downlink resources is employed. As further described in subsection 5.2.2 of the 3GPP technical specification the L1 layer is responsible for error detection on transport channels and indication to higher layer, FEC (Forward Error Correction) encoding/decoding and interleaving/deinterleaving of transport channels.
Packet Data Convergence Protocol, PDCP, provides mapping between Network PDUs (Protocol Data Units) of a network protocol, e.g. the Internet protocol, to an RLC entity. PDCP compresses and decompresses redundant Network PDU control information (header compression and decompression).
For transmissions on point-to-multipoint logical channels, Broadcast/Multicast Control, BMC, stores at UTRAN-side Broadcast Messages received from an RNC, calculates the required transmission rate and requests for the appropriate channel resources. It receives scheduling information from the RNC, and generates schedule messages. For transmission, the messages are mapped on a point-to-multipoint logical channel. At the UE side, BMC evaluates the schedule messages and deliver Broadcast Messages to upper layer in the UE.
3G TS 25.301 also describes protocol termination, i.e. in which node of the UTRAN the radio interface protocols are terminated, or equivalently, where within UTRAN the respective protocol services are accessible.
FIG. 3 illustrates a DSCH and FACH protocol model in accordance with 3GPP TS 25.301. The figure illustrates schematically two respective RNC entities of a Serving RNC and a Controlling RNC. As already mentioned, the Serving RNC and Controlling RNC can be separate or co-incident. In case of separate RNCs they communicate over an Iur interface, otherwise they communicate locally. An RNC comprises an RLC entity including an L2/RLC protocol layer >>L2/RLC<< at UTRAN side in FIG. 2. In FIG. 3, RLC entities >>RLC S<< and >>RLC C<< are entities of the Serving RNC and Controlling RNC respectively. In the figure there are two MAC-entities >>MAC-d<<, >>MAC-c/-sh<< illustrated routing dedicated channels over common or shared channels. MAC-d resides in the Serving RNC and MAC-c/-sh in the Controlling RNC. The routing comprises buffering of data in the MAC-entities >>MAC-d<< and >>MAC-c/-sh<<, to accommodate for the unsynchronized data flows into and out of MAC-d and MAC-c/-sh. The two MAC-entities are responsible for the L2/MAC protocol layer functionality at UTRAN side according to FIG. 2. The simplified protocol model in FIG. 3 is illustrated for a DSCH (Downlink Shared Channel), being a shared transport channel, and an FACH (Forward Link Access Channel), being an example of a common transport channel, from Node B to a user equipment, UE. Within UMTS the interface between Node B and UE is called Uu.
3rd Generation Partnership Project (3GPP): Technical Specification Group Radio Access Network, RLC Protocol Specification, 3G TS 25.322 v3.5.0, France, December 2000, specifies the RLC protocol. The RLC layer provides three services to the higher layers:                transparent data transfer service,        unacknowledged data transfer service, and        acknowledged data transfer service.        
In subsection 4.2.1.3 an acknowledged mode entity, AM-entity, is described (see FIG. 4.4 of the 3GPP Technical Specification). In acknowledged mode automatic repeat request, ARQ, is used. The RLC sub-layer provides ARQ functionality closely coupled with the radio transmission technique used.
Higher layer applications can be, e.g., applications on the Internet. Most applications on the Internet use protocols, such as TCP (Transport Control Protocol), that controls the transmission rate, based on link quality in terms of packet loss and delay characteristics. Consequently, besides the negative effect of retransmission delays as such on perceived quality, substantial queuing delay can also lead to secondary effects further reducing quality of service.
None of the cited documents above discloses a method and system of eliminating or reducing retransmissions due to route switching data losses, or flow control for route switching eliminating or reducing buffering, particularly inside of an ARQ loop.